In a communication system, a transmitting device sends a frame of data to a receiving device. When receiving a frame, there can be significant delay between the time that the last bit of a frame is received over the air and the time that it is determined whether there was an error in the frame which can result in inefficient use of the channel.
There are a number of reasons for this latency. Several procedures can be performed by hardware, software, or a combination, to prepare received information for further processing and check for errors in the frame. These procedures typically include, for example, de-interleaving, de-whitening, and forward error correction such as Viterbi decoding. Depending on the protocol, other checks such as a CRC (cyclic redundancy check) or similar can be performed in addition to the de-interleaving, whitening, and decoding, to further determine whether there was an error. These procedures are sometimes collectively referred to as a “frame check sequence” (FCS).
Each of these procedures takes a certain amount of time before it can determine whether a frame has an error. While the de-whitening does not introduce significant time, the Viterbi decoder can be responsible for much of the delay. There can be a significant time from when the last bit of the frame is received over the air until it is decided whether the frame was received without error.
Certain protocols such as IEEE 802.15.3 provide for the receiving device to transmit a positive acknowledgement to the transmitting device when there is an error in the frame. However, according to the 802.15.3 protocol, if there is an error, the transmitting device does not expect to receive any particular response. Nevertheless, the transmitting device can await the possible receipt of a positive acknowledgement.
An ultra wide band (UWB) physical layer can turn around very quickly from to transmit. Nevertheless, the receive check processing described above adds latency and introduces unproductive dead air time.